The disclosure relates to an image reader that reads an image from a document, and more particularly, pertains to an image reader in which a predetermined initialization operation can be omitted.
An image reader is commonly provided on, for example, a copying machine, a facsimile machine, and an a multifunctional machine. Conventionally, the image reader includes a read head that reads a document, and performs a predetermined initialization operation before performing an operation of reading an image from a document. In some cases, however, the read head may be in a standby status at a position that is displaced from a normal standby position because some problem or error occurred at a previous reading operation. If the reading operation is performed with nothing done with the displacement of the read head, the read head may read an image from a document at a position that is displaced from an appropriate image read position. The displacement of the read head may cause displacements or slur of a read image. To avoid such problems, the initialization operation is conventionally performed to return the read head to a read reference position before a next reading operation is started.
When the above-described initialization operation is performed before a reading operation is performed, however, a waiting time occurs until the reading operation starts. If the initialization operation is performed every time the execution of a reading operation is instructed, a total processing time will be extended. In addition, some other problems may arise. For example, power consumption in the image reader may increase and performance of members arranged in the image reader may be reduced. To resolve such problems, there has been known various techniques of omitting the predetermined initialization operation in order to reduce the processing time and the power consumption.
For example, Japanese Laid-Open Patent Publication No. 2003-75933 discloses an image forming apparatus including a document read portion, wherein the document read portion is capable of sliding with respect to a body of the image forming apparatus. The image forming apparatus further includes a home position (HP) sensor and a contact image sensor (CIS), which reads a document. The HP sensor is used to detect the CIS for positioning the CIS at a read starting position. When the HP sensor is on, the CIS is located at the read starting position. In this case, an initialization operation for returning the CIS to the read starting position is omitted even immediately after power of the image forming apparatus is turned on.